1. Field of the Invention
The present invention relates to a thin-film magnetic head which performs a recording action by supplying a magnetic field to a recording medium.
2. Related Background Art
As is well known, a conventional thin-film magnetic head such as a perpendicular magnetic recording head, for example, has a main magnetic pole layer and a return path layer which are laminated with a nonmagnetic layer interposed therebetween on a surface opposing a recording medium, and a coil layer which supplies a recording magnetic field to the main magnetic pole layer and return path layer. The main magnetic pole layer exposed at the medium-opposing surface has an area sufficiently smaller than that of the return path layer, while the main magnetic pole layer and return path layer are magnetically coupled to each other on the deeper side in the height direction. For making it possible to locally apply a strong recording magnetic field to the recording medium, the main magnetic pole layer has a pole straight part exposed at the medium-opposing surface and a flare part in contact with the pole straight part on the deeper side in the height direction. When the coil layer is energized, the recording magnetic field is induced between the main magnetic pole layer and return path layer, perpendicularly enters a hard film of the recording medium from a leading end face of the main magnetic pole layer exposed at the medium-opposing surface, and returns to the return path layer through a soft film of the recording medium. This performs magnetic recording at a part opposing the main magnetic pole layer.
When the main magnetic pole layer to become a yoke has such a domain structure as to yield a greater magnetization component in the height direction in the thin-film magnetic head, the yoke domain is transferred to the main magnetic pole layer leading end, whereby the remanent magnetization in the magnetic pole increases. In the thin-film magnetic head, the magnetization is narrowed by the yoke form of the main magnetic pole layer. For narrowing the magnetization, the flare angle of 45° in the flare part has been considered the most efficient. Therefore, the flare angle of the flare part has conventionally been determined within a typical range of 15° to 45° with side fringes in mind. When the flare part has two stages, the flare angle in the second stage has been made wider (greater) than that in the first stage, so as to regulate the narrowing of magnetization.
(A) and (B) of FIG. 7 are views showing a main magnetic pole layer 210 having a first flare part 210B and a second flare part 210C, which are conventional two-stage flare parts, as seen two-dimensionally. In these drawings, X, X, and Z directions are defined by the track width direction, the height direction, and the laminating direction of layers constituting a thin-film magnetic head or the moving direction of a recording medium, respectively. The first flare part 210B subsequent to the pole straight part 210A has a flare angle of 20° to 45°. When a base part 210D acting as a yoke part becomes a closure domain as in (A) of FIG. 7, a strong magnetic field is applied to a magnetic pole leading end 210a, since the base part 210D has a large magnetization component in the height direction, whereby strong PE (pole erasure) occurs. When the base part 210D becomes a laterally striped domain as shown in (B) of FIG. 7, on the other hand, the magnetization component in the height direction of the domain of the yoke part is small, so that the magnetic field applied to the magnetic pole leading end 210a becomes weak, thereby lowering PE. When the yoke form/magnetic anisotropy is uncontrolled as such, the effective magnetization (illustrated by whitened arrows) additionally applied to the magnetic pole leading end 210a varies greatly, whereby the occurrence of PE cannot be suppressed.
Therefore, it has conventionally been proposed to widen the main magnetic pole layer in the track width direction, e.g., set the ratio of width/length in the height direction to 1 or greater, so as to control the domain structure (Japanese Patent Application Laid-Open No. 2006-155867).